The present invention concerns an aircraft landing gear. More particularly, but not exclusively, this invention concerns an aircraft landing gear comprising an inboard sidestay assembly and an aircraft including such a landing gear.
In certain aircraft the main landing gear is mounted on the wing. The wing structure must have sufficient strength to react the landing gear loads at the point or points to which the landing gear attaches. This may limit the choice of materials that can be used in construction and/or lead to the need for the structure to be reinforced, thereby increasing the weight of the aircraft. This is a particular issue for wings using composite materials, for example Carbon Fibre Reinforced Polymer (CFRP) wings, as these materials are typically anisotropic. For example, CFRP materials can withstand higher loading along the fibre length, but may require substantial reinforcement to accommodate off-axis loads. Loads that may be accommodated by a metal structure may therefore require addition reinforcement when that same structure is made using a composite. This may increase the weight of the structure and/or lead to manufacturing difficulties when attempting to lay up composite regions which are very thick, or which have a complicated shape. It would therefore be desirable to provide a landing gear that results in an improved load profile, for example a reduction in the maximum load experienced at the point(s) of attachment to the wing and/or a reduction in off-axis loads transmitted to the wing structure.
One prior art method of reducing the loads experienced at any one point of attachment is to provide a landing gear which transfers loads from the landing gear to the aircraft over multiple attachment points including points on both the wing and the fuselage. EP 0 031 602 describes such a landing gear which is attached to the aircraft at four points, namely via two trunnion bearings at the top of the main strut attaching the landing gear to the wing, a drag strut and a side strut attaching the landing gear to the wing/body. While this four-point structure may produce some loads reduction, significant off axis loads are still transferred to the wing. In particular, when drag loads are transmitted to the wing via the two trunnion bearings (also known as fore and aft pinions) this generates a significant bending movement between the two trunnion joints in the wing.
Typically, modern landing gears are retracted once the aircraft is in flight. Space is at a premium within the envelope of the aircraft and accordingly it is desirable that a landing gear can be retracted into a compact configuration. However, many multiple attachment point landing gears are not particularly compact when retracted and/or are mechanically complex thereby increasing manufacture and/or maintenance costs. It would be advantageous to provide a mechanically simple landing gear that can reduce the landing gear loads transferred to the wing of the aircraft while maintaining a compact configuration when retracted.
The present invention seeks to mitigate one or more of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved landing gear.